The present invention relates to the field of bags having complementary closure strips that are actuated by a cursor both for opening and for closing.
Such bags are described, for example, in documents EP-A-0 051 010, EP-A-0 102 301, and EP-A-0 479 661.
Those bags that are cursor-actuated both for opening and for closing have already given good service.
The cursors make the bags easier to open and close. The presence of a cursor is particularly appreciated by the elderly and the visually handicapped.
Nevertheless, most known bags with cursors do not give full satisfaction. In particular, most such bags are not totally leakproof when the strips are in the closed position. This lack of sealing is due to the fact that the strips remain separate ahead of the cursor.
Nevertheless, leakproofing is required in numerous applications, particularly, but not exclusively, for bags that are used for freezing foodstuffs.
Attempts have been made to remedy that drawback by proposing closure strips that present a local discontinuity in the vicinity of the end which receives the cursor when the bag is in the closed position, such that the cursor penetrates into the discontinuity and ensures that the strips are perfectly engaged in one another over their entire length when in the closed position.
Nevertheless, the means proposed in that context turn out to be very complex. Even so, they do not always ensure that the bags are perfectly sealed. In addition, they suffer from the major drawback of not retaining the cursor reliably and consequently of running the risk of the cursor being swallowed by small children, for example.
The object of the present invention is to improve the performance of known cursor-fitted bags.
The main object of the present invention is to propose bags presenting leakproofing that is better than that of previously known bags.
Another object of the present invention is to propose means that reduce the risk of the cursor being removed by mistake, specifically in order to reduce the risk of the cursor being swallowed by young children.
Another object of the present invention is to propose means enabling bags to be produced automatically and at a high rate of throughput.
In the context of the present invention, these objects are achieved by a bag comprising two generally parallel sheets forming the main walls of the bag, complementary closure strips fixed to respective ones of the sheets, and a cursor for actuating the strips for closing and opening purposes, the bag being characterized in that it further comprises, parallel to the closure strips, between said sheets, and level with the mouth of the bag, additional means in relief disposed on the insides of the closure strips, designed to provide sealing by forming a barrier between the sheets in the closed position of the bag, said additional means in relief being adapted to be urged towards their sealing position by the cursor when the cursor is moved towards its position for closing the bag.
In certain embodiments, said additional means in relief are placed facing the flanks of the cursor.
As specified in greater detail below, such additional means in relief can be formed, for example, by means of at least one bead secured to the inside surface of a sheet of the bag, or by means of two symmetrical beads secured to the respective inside surfaces of the two sheets of the bag, or indeed by means of complementary male/female elements secured to respective inside surfaces of the two sheets of the bag.
According to another advantageous characteristic of the present invention, the bag, in the vicinity of its mouth includes means situated on the side of the closure strips opposite from the side on which said additional leakproofing means are situated, and adapted to define thrust between opposing inside faces of the walls of the bag, and means are provided on the cursor to urge the walls of the bag inwards in a zone of said walls lying between the additional leakproofing means and the thrust means. This guarantees that said additional means are urged into a sealing position by the cursor. This urging is preferably performed in register with the closure strips.
The present invention also provides films fitted with such sealing means and such closure strips, and also extruded tapes carrying such means.
According to another advantageous characteristic of the present invention, the bag comprises two generally parallel sheets forming the main walls of the bag, complementary closure strips fixed to respective ones of said sheets in the vicinity of the mouth of the bag, and a cursor having two side flanges interconnected by a web, the flanges being placed on the outsides of the sheets at the mouth of the bag and co-operating with a central elongate tongue to define two converging passages for the complementary closure strips, and the bag is characterized by the fact that the tongue is interrupted so as to be set back from the longitudinal end of the cursor, at least at the wider end of the cursor corresponding to the diverging ends of the passages, and that the side flanges are provided in the vicinity of their free edges remote from the web with urging means for urging the sheets of the bag towards each other, said means occupying the entire longitudinal extent of the tongue and extending longitudinally beyond each end thereof so as to ensure that the bag is leakproof when it is in its closed position.